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    <title>Sentinel Toolbox Help - Performance parameters</title>
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<table class="header">
    <tr class="header">
        <td class="header">&nbsp;
            Performance parameters
        </td>

        <td class="header" align="right"><a
                href="nbdocs://org.esa.snap.snap.help/org/esa/snap/snap/help/docs/general/overview/SnapOverview.html"><img
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<h3>S3TBX Options</h3>

<p>

</p>

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<h4><a name="systemParameters">Sentinel-3 Readers</a></h4>

<h5>SLSTR</h5>
<ul>
    <li><b>Read Sentinel-3 SLSTR L1B products with per-pixel geo-codings instead of using tie-points</b><br>
        Sentinel-3 SLSTR L1B products contain tie point grids and, for each of the eight different grid types,
        per-pixel geo-codings.
        Spatial locations per pixel can be derived from both, however, the result might vary slightly.
        When using tie-point geo-coding, the product is opened quicker and the pixel locations are more similar across
        different grids, using per-pixel geo-codings will lead to more precise results.
    </li>
    <li><b>Load orphan pixels of Sentinel-3 SLSTR L1B products</b><br>
        If selected, orphaned SLSTR L1B pixels will be read as extra bands.
        In the product explorer, they are found in the *orphan* subfolder.
    </li>
    <li><b>Read Sentinel-3 SLSTR L1B product with custom calibration</b><br>
        This option provides a way to set scaling factors, offsets, and adjustment factors to SLSTR L1B bands.
        The three values will be combined like this:<br><br>

        <p><code>value = ((raw_value * factor) + offset) * adjustment_factor</code></p>

        When switched on, the S3TBX will consider factors, offsets and adjustment factors given in the <i><b>s3tbx.properties</b></i> file.<br/>
        <i><b>Please see the note below on where to find this file.</b></i><br><br>
        Factors and offsets can be set to each band.<br>
        To set a factor, add a line like this:<br><br>

        <p><code>s3tbx.reader.slstrl1b.<b>xx</b>.calibration.factor = 2.0</code></p>

        Likewise, offsets are set like this:<br>

        <p><code>s3tbx.reader.slstrl1b.xx.calibration.offset = 0.5</code></p>

        and adjustment factors like this:<br>

        <p><code>s3tbx.reader.slstrl1b.xx.calibration.adjustment_factor = 1.2</code></p>

        Where <b>xx</b> is to be replaced by any bandname in lowercase.

        Note that possibly pre-existing scaling factors or offsets, defined by the Sentinel-3 product will be replaced.
    </li>
    <li><b>Apply S3MPC recommendation to adjust SLSTR L1B S5 and S6 radiometric calibration</b><br>
        When this option is set, the bands S5 and S6 from a SLSTR L1B product are re-calibrated
        with the following adjustment factors:
        <ul>
            <li>S5 for Nadir View: 1.12</li>
            <li>S6 for Nadir View: 1.2</li>
            <li>S5 for Oblique View: 1.15</li>
            <li>S6 for Oblique View: 1.26</li>
        </ul>
        These values are the adjustment factors recommended by the S3MPC.
        To use other factors, uncheck this box and define others using SLSTR L1B custom calibration.
    </li>
    <li><b>Read Sentinel-3 SLSTR L2C products with per-pixel geo-codings instead of using tie-points</b><br>
        Sentinel-3 SLSTR L2C products contain tie point grids and, for each of the two different grid types,
        per-pixel geo-codings.
        Spatial locations per pixel can be derived from both, however, the result might vary slightly.
        When using tie-point geo-coding, the product is opened quicker and the pixel locations are more similar across
        the different grids, using per-pixel geo-codings will lead to more precise results.
    </li>
</ul>
<h5>OLCI</h5>
<ul>
    <li><b>Read Sentinel-3 OLCI products with per-pixel geo-coding instead of using tie-points</b><br>
        Sentinel-3 OLCI products contain tie point grids and a per-pixel geo-coding.
        Spatial locations per pixel can be derived from both, however, the result might vary slightly.
        When using tie-point geo-coding, the product is opened quicker,
        using the per-pixel geo-coding will lead to more precise results.
    </li>
    <li><b>Read Sentinel-3 OLCI L1 product with custom calibration</b><br>
        This option provides a way to set scaling factors and offsets to OLCI L1 bands.
        When switched on, the S3TBX will consider factors and offsets given in the <i><b>s3tbx.properties</b></i> file.<br>
        <i><b>Please see the note below on where to find this file.</b></i><br><br>
        Factors and offsets can be set to any band.<br>
        To set a factor, add a line like this:<br><br>

        <p><code>s3tbx.reader.olcil1.xx.calibration.factor = 2.0</code></p>

        where xx is to be replaced by the name of the band in lowercase.
        Likewise, offsets are set like this:<br><br>

        <p><code>s3tbx.reader.olcil1.xx.calibration.offset = 0.5</code></p>

        Note that possibly pre-existing scaling factors or offsets, defined by the Sentinel-3 product will be replaced.
    </li>
</ul>
<h5>MERIS</h5>
<ul>
    <li><b>Read ENVISAT MERIS products in SAFE format with per-pixel geo-coding instead of using tie-points</b><br>
        ENVISAT MERIS products in SAFE format contain tie point grids and a per-pixel geo-coding.
        Spatial locations per pixel can be derived from both, however, the result might vary slightly.
        When using tie-point geo-coding, the product is opened quicker,
        using the per-pixel geo-coding will lead to more precise results.
    </li>
</ul>

<h4><b>NOTE:</b> s3tbx.properties file</h4>
<p>The <i><b>s3tbx.properties</b></i> file let's users specify special properties for the Sentinel-3 Toolbox. There are two locations where this file
    can be defined. At both places, if the file does not yet exist it can simply be created as a plain text
    file.
</p>
<p>One is located within the SNAP installation directory in the <i><b>etc</b></i> folder and defines the properties for the installed SNAP instance.
    Here you need usually admin right to modify the file.<br>
    The other is located in the <i><b>.snap/etc</b></i> folder within the user's home directory.
    The second, in the user directory defines the settings per user and overrules the ones in the installation directory.
</p>
<p>Depending on the operating system and your settings the <i><b>.snap</b></i> folder might not be visible to you.
    You can do the following to make it visible:
</p>
<table>
    <thead>
    <tr>
        <th>OS</th>
        <th>Action</th>
    </tr>
    </thead>
    <tr>
        <td>Windows</td>
        <td>Nothing to do. The directory is visible by default.</td>
    </tr>
    <tr>
        <td>Linux</td>
        <td>On the command line you nee to type <code>ls -la</code> to see the directory. In a file explorer like the one of Ubuntu you need to make
            sure that in the settings the display of hidden files is enabled.
        </td>
    </tr>
    <tr>
        <td>Mac</td>
        <td>Since macOS Sierra (10.12) you can press <code>&lt;CMD&gt; + &lt;SHIFT&gt; + &lt;.&gt;</code> in finder to make the directory visible.
            Prior this version you can nivagate to the user directory and then press <code>&lt;CMD&gt; + &lt;SHIFT&gt; + &lt;G&gt;</code>. This brings
            up an input dialog where you can enter the folder name <i><b>.snap</b></i>. On enter you will be navigated to this directory.
        </td>
    </tr>
</table>


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